Fluorometric method for monitoring surface additives in a papermaking process

ABSTRACT

A method of monitoring and optionally controlling the addition of one or more surface additives to a papermaking process via fluorometric means is disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/942,065, which is herein incorporated by reference.

FIELD OF THE INVENTION

This invention pertains to monitoring and optionally controlling theaddition of one or more surface additives to a papermaking process.

BACKGROUND OF THE INVENTION

Current practice for measuring the amount of surface additive(s) usuallyconsists of a manual technique of sheet disintegration and/or massbalance calculations that are relative in nature.

In the case of starch pickup at the size press, a papermaker (e.g. aboardmaker) will in many cases grossly over apply the amount of starchadded to a papermaking process, in order to ensure enough starch is heldon the surface of the sheet for the functional intent Past trialsincluded metering size press applications, which allowed the reductionof starch via a blade application technique. While this allowed asignificant reduction of starch in the range of 50-70%, the riskassociated with failures due to unpredicted and uncontrolled variationsof starch pickup was too great to overcome. As a result, manypapermakers reverted to puddle style size presses in order to ensureenough starch was added to the sheet.

A more accurate and timely measurement of the amount of surfaceadditives on a sheet is therefore desired. This potentially will allowthe papermaker to drive addition rates to very low levels, while beingable to quickly predict and control statistically out of specificationaddition rates.

SUMMARY OF THE INVENTION

The present disclosure provides for a method of monitoring andoptionally controlling the addition of one or more surface additives toa papermaking process comprising the following steps: (a) adding a knownamount of one or more surface additives to a papermaking process eitheralone or in known proportion with a known amount of one or more inertfluorescent tracers, wherein the surface additives can only be addedalone when the surface additives are capable of fluorescing; (b)measuring the fluorescence of the surface additives and/or one or moreinert fluorescent tracers at a point subsequent to adding the surfaceadditives and after a sheet has been formed, wherein the surfaceadditives can only be measured when they are capable of fluorescing andwherein fluorescence is measured with a reflectance based fluorometer;(c) correlating the amount of fluorescence of the surface additives whenthey are capable of fluorescing and/or inert fluorescent tracers on asheet with the concentration of the surface additives in a coating on asheet and/or thickness of a coating on a sheet; and (d) optionallycontrolling the addition of one or more surface additives to apapermaking process by adjusting the amount of the surface additivesadded to the papermaking process in response to the coating thickness ona sheet and/or concentration of the surface additives in a coating on asheet.

A method of monitoring and optionally controlling the addition of one ormore surface additives to a papermaking process comprising the followingsteps: a) adding a known amount of a composition containing one or moresurface additives to a papermaking process either alone or in knownproportion with a known amount of one or more inert fluorescent tracers,wherein the composition containing the surface additives can only beadded alone when the surface additives are capable of fluorescing; b)measuring the fluorescence of the surface additives and/or one or moreinert fluorescent tracers at a point prior to sheet formation; c)optionally measuring the fluorescence of the composition containing thesurface additives and/or one or more inert fluorescent tracers at apoint subsequent to adding the surface additives and after a sheet hasbeen formed, wherein the surface additives can only be measured whenthey are capable of fluorescing and wherein fluorescence is measuredwith a reflectance based fluorometer; d) correlating the amount offluorescence of the surface additives when they are capable offluorescing and/or inert fluorescent tracers with the concentration ofthe surface additives, and if step c) occurs, then correlating theamount of fluorescence of the surface additives when they are capable offluorescing and/or inert fluorescent tracers on a sheet with theconcentration of the surface additives in a coating on a sheet and/orthickness of a coating on a sheet; and e) optionally controlling theaddition of the composition containing one or more surface additives toa papermaking process by adjusting the amount of the surface additivesadded to the papermaking process in response to the concentration of thesurface additives, and if step c) occurs, then optionally controllingthe addition of the composition containing one or more surface additivesto a papermaking process by adjusting the amount of the surfaceadditives added to the papermaking process in response to the coatingthickness on a sheet and/or concentration of the surface additives in acoating on a sheet.

A method of monitoring and optionally controlling the addition of one ormore surface additives to a papermaking process comprising the followingsteps: a) adding a known amount of a composition containing one or moresurface additives to a papermaking process either alone or in knownproportion with a known amount of one or more inert fluorescent tracers,wherein the composition containing the surface additives can only beadded alone when the surface additives are capable of fluorescing; b)measuring the fluorescence of the surface additives and/or one or moreinert fluorescent tracers in an apparatus that serves to hold or feed orapply an aqueous composition into said papermaking process; c)optionally measuring the fluorescence of the composition containing thesurface additives and/or one or more inert fluorescent tracers at apoint subsequent to adding the surface additives and after a sheet hasbeen formed, wherein the surface additives can only be measured whenthey are capable of fluorescing and wherein fluorescence is measuredwith a reflectance based fluorometer; d) correlating the amount offluorescence of the surface additives when they are capable offluorescing and/or inert fluorescent tracers with the concentration ofthe surface additives, and if step c) occurs, then correlating theamount of fluorescence of the surface additives when they are capable offluorescing and/or inert fluorescent tracers on a sheet with theconcentration of the surface additives in a coating on a sheet and/orthickness of a coating on a sheet; and e) optionally controlling theaddition of a composition containing one or more surface additives to apapermaking process by adjusting the amount of the surface additivesadded to the papermaking process in response to the concentration of thesurface additives; and if step c) occurs, then optionally controllingthe addition of a composition containing one or more surface additivesto a papermaking process by adjusting the concentration of the surfaceadditives in the apparatus in response to coating thickness on a sheetand/or concentration of the surface additives in a coating on a sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of how a reflectance-based fluorometer wouldwork in one embodiment of the invention.

FIG. 2 shows a graph of individual fluorescence vs. individual starchdry pick-up shown by a starch and inert fluorescent tracer combination.

DETAILED DESCRIPTION OF THE INVENTION DEFINITIONS

“Papermaking process”/“papermaking processes” refer to a method(s) ofmaking any kind of paper products (e.g. paper, tissue, board, etc.) frompulp comprising forming an aqueous cellulosic papermaking furnish,draining the furnish to form a sheet and drying the sheet. The steps offorming the papermaking furnish, draining and drying may be carried outin any conventional manner generally known to those skilled in the art.The papermaking process/processes may also include a pulping stage, i.e.making pulp from woody raw material and bleaching stage, i.e. chemicaltreatment of the pulp for brightness improvement. Moreover, thepapermaking process includes all processing steps applied to a papersheet up till the end-user receives and optionally analyzes the papersheet prior to use of the paper product.

“Sheet” “sheets” refer to sheet(s) formed as a result of or during apapermaking process/papermaking processes.

“Surface additive”/“surface additives” refer to papermaking additive(s)that impart one or more chemical and/or physical (e.g. mechanical)properties on a sheet surface. For example, the sheet can be a papersheet, tissue sheet, board sheet, or any other type of sheet produced bya papermaking process. For example, an imparted chemical property mayallow “ink” to bind to the paper in a more efficacious manner.

“NADH” refers to Nicotinamide Adenine Dinucleotide, reduced, and/orderivatives thereof.

“ATP” means Adenosine Tri-Phosphate.

Preferred Embodiments

As described above, one or more surface additives added to a papermakingprocess are tracked by a fluorometrie-based protocol. This requires thatthe medium exposed to fluorescence is suitable for fluorometricmeasurement, e.g. the entire film depth of a coating is excited and itsemission collected. One of ordinary skill in the art could determinethis without undue experimentation.

The fluorometric protocol includes the following approaches: (1) the oneor more surface additives are capable of fluorescing, inherent and/ormodified to fluoresce, e.g. with a fluorescent moiety or by reactingwith an in-system molecule or by other means aside from inherentcharacteristics, (2) one or more inert fluorescent tracers are added inknown proportion with the surface additives, or (3) a combinationthereof.

When a surface additive is capable of fluorescing, the fluorescence canbe directly correlated to the concentration of the surface additive in acoating/thickness of a coating containing the surface additive, e.g. bycalibrating fluorescence intensity with the concentration of the surfaceadditive and/or thickness of a coating containing the surface additive.One of ordinary skill in the art could carry out this procedure withoutundue experimentation.

In one embodiment, the surface additives are inherently fluorescent.

In another embodiment, a fluorescent moiety can be covalently attachedto the non-fluorescent surface additives. Therefore, the functionalizedsurface additives have fluorescent properties.

When an inert fluorescent tracer is involved, the inert fluorescenttracer is added in known proportion with the surface additive. Theamount of surface additive or thickness of a coating containing asurface additive can be inferred from the fluorescence of the inertfluorescent tracer, e.g. by calibrating fluorescence intensity withconcentration of the additive in a coating on a sheet and/or thicknessof a coating containing the additive on a sheet. One of ordinary skillin the art could carry out this procedure without undue experimentation.

In one embodiment, the inert fluorescent tracers can be added to acoating formulation at a specific known concentration such that bymeasuring the concentration of inert fluorescent tracers, the amount ofthe coating on a sheet or surface additives in a coating on a sheet canbe inferred.

It may also be possible to monitor both a surface additive that isfluorescent and an inert fluorescent tracer. The amount of the coatingon a sheet or surface additives in a coating on a sheet can be inferredfrom the fluorescence of the inert fluorescent tracer and fluorescenceof the surface additive, by calibrating fluorescence intensity withconcentration of the additive in a coating on a sheet and/or thicknessof a coating containing the additive on a sheet. One of ordinary skillin the art could carry out this procedure without undue experimentation.

Various types of one or more inert fluorescent tracers may be utilizedfor this invention.

One of ordinary skill in the art would know what an inert fluorescenttracer is.

In one embodiment, an inert fluorescent tracer is a substance, which ischemically non-reactive with any components in the papermaking processand does not itself degrade with time. It is completely soluble in thesystem at all relevant levels of concentration. Its fluorescenceintensity is always/substantially proportional to its concentration andis not quenched or otherwise diminished by the system.

In another embodiment, an inert fluorescent tracer is an inertfluorescent tracer that is not appreciably or significantly affected byany other chemistry in a papermaking process. To quantify what is meantby “not appreciably or significantly affected”, this statement meansthat an inert fluorescent compound has no more than a 10% change in itsfluorescent signal, under conditions normally encountered in papermakingprocess. Conditions normally encountered in a papermaking process areknown to people of ordinary skill in the art of a papermaking process.

In another embodiment, the desired characteristics for an inertfluorescent tracer, preferably include: high water solubility, excellentchemical stability, good fluorescence properties at manageablewavelengths (e.g. not be quenched by other additives in the sheet/papersheetboard components), and can be monitored in the presence of commonoptical brightening agents, e.g. outside the wavelength of opticalbrighteners to prevent interference between optical brighteners andinert fluorescent tracers.

In another embodiment, the inert fluorescent tracer is a FDA-approvedtracer, which is required, for example, in food packaging.

In one embodiment, one or more inert fluorescent tracers are selectedfrom the group consisting of at least one of the following: fluoresceinor fluorescein derivatives, rhodamine or rhodamine derivatives, asulfonate salt of naphthalene, a sulfonate salt of pyrene, a sulfonatesalt of stilbene, a sulfonate salt of biphenyl, phenylalanine,tryptophan, tyrosine, vitamin A (retinol), vitamin B2 (riboflavin),vitamin B6 (pyridoxin), vitamin E (α-tocopherols), NADH, ATP,ethoxyquin, caffeine, vanillin, naphthalene sulfonate formaldehydecondensate, a phenyl sulfonate formaldehyde condensate, sulfonatedlignin, a polymer containing at least one of the following moietiesnaphthalene sulfonates, pyrene sulfonates, biphenyl sulfonates, orstilbene sulfonates.

Depending on the papermaking process, the optimum concentration of inertfluorescent tracers will vary. One of ordinary skill in the art candetermine the amount of inert fluorescent tracers without undueexperimentation. Preferably, e.g., in the case of starch, higherconcentrations of inert fluorescent tracers work better than lowerconcentrations of inert fluorescent tracers.

When measuring a paper sheet or solid surface, the fluorometer utilizedshould be a reflectance-based fluorometer since it is desired todetermine the thickness of an applied thin coating onto the surface ofan opaque sheet. One or more may be utilized.

A reflectance-based fluorometer is available from Nalco Company or OceanOptics, Dunedin, Fla.

A diagram of one embodiment of a reflectance-based fluorometer is givenin FIG. 1.

The reflectance fluorometer uses an optical fiber to excite the traceron a sheet and monitor its reflected fluorescence. A suitable lightsource, such as an LED, xenon flash lamp or discharge lamp provides theexcitation light. The raw source light is filtered by a suitableexcitation filter (available from Semrock, Inc./Andover, Inc.) to removeunwanted wavelengths in the fluorescence emission region. The light isreflected at 90 degrees and additionally filtered by a dichroic filterto give a new beam along a different direction. The beam is focused ontothe core of a fiber optic cable by an appropriate lens. The other end ofthe fiber optic is positioned close to or touching the surface of thepaper sheet in order to illuminate a region of its surface causingfluorescence emission. The emission is captured by the same fiber whichcarries the reflected light back to the lens where it is collimated anddirected back onto the dicbroic filter. Reflected excitation light isreflected back to the source while the fluorescence passes straightthrough to an emission filter. A suitable optical detector, such as aphotodiode or photomultiplier tube, detects the filtered light. Anoptional reference detector can be used to correct for varying lightsource intensity.

Other designs for reflectance-based fluorometers would be apparent toone of ordinary skill in the art.

Other types of fluorometers may be utilized, especially in cases wherefluorescence of a non-solid surface is measured.

In one embodiment, a handheld or benchtop fluorometer can be used whenmeasuring the wet-end of a papermaking process prior to sheet formationor when one is measuring fluorescence of an aqueous composition ofsurface additives in an apparatus wherein the sample is collected andput into a cuvette that is inserted into the fluorometer. Alternatively,a fiber optic based handheld or benchtop fluorometer can be used whereinthe probe is immersed in the collected sample for a fluorescencereading.

In another embodiment, an in-line fluorometer can be used when measuringthe wet-end of a papermaking process prior to sheet formation or whenone is measuring fluorescence of an aqueous composition of surfaceadditives in an apparatus wherein the sample flows through a suitableflow cell in which sample fluorescence can be continuously measured.Alternatively, a fiber optic based, in-line fluorometer can be usedwherein the probe is mounted such that it is immersed in the sample ormounted in a flow cell for a fluorescence measurement.

Various types of surface additives may be utilized in the presentinvention.

In one embodiment, the surface additives are selected from the groupconsisting of at least one of the following: starch, pigments, binders,plasticizers, and other additives to improve the physical properties ofa paper/board sheet, including surface strength, brightness,printability, water resistance, or adhesion of subsequent coatings.

In another embodiment, the surface additives contain a covalently bondedfluorescent moiety.

In another embodiment, the starch contains a covalently bondedfluorescent moiety.

The surface additives may be added at various stages in the papermakingprocess.

In one embodiment, the surface additives are added between a formingsection of a papermaking process and a press section of a papermakingprocess.

In another embodiment, the surface additives are added at the wet-end ofa papermaking process.

In another embodiment, the surface additives are added to a papermakingprocess between or at a water box and a sheet.

The fluorescence of the sheet may be measured at various points in thepapermaking process.

In one embodiment, the fluorescence is measured at some point after thepress section.

In another embodiment, the fluorescence is measured after the dryersection of a papermaking process.

In another embodiment, the fluorescence is measured after a dry line ina forming section.

In another embodiment, the fluorescence is measured proximate to thepress section.

In another embodiment, the fluorescence is measured in a papermakingprocess after a paper is converted to a narrow web or a sheet before enduse.

In another embodiment, the fluorescence of starch containing acovalently bonded fluorescent moiety and/or fluorescence of inertfluorescent tracers added in known proportion with the starch ismeasured after a dryer section and before a coating section of apapermaking process.

In another embodiment, the fluorescence of the surface additives and/orfluorescence of inert fluorescent tracers added in known proportion withsaid surface additives, excluding starch, are measured after the coatingsection of a papermaking process.

Fluorescence may be measured at a fixed point (one point), e.g. ameasurement in the machine-direction, or at plurality of points, e.g.scanning a plurality of points across the sheet in a cross-directionalmanner relative to the direction of travel of the paper sheet. Areflectance fluorometer may be utilized in various ways to carry outthis task. One of ordinary skill in the art would appreciate variousways of carrying out this task.

In one embodiment, the fluorescence is measured at one point or aplurality of points.

In another embodiment, the fluorometer may be configured to measure inthe machine direction, e.g. positioned at a fixed point.

In another embodiment, the measurement of a plurality of points occursby scanning a fluorometer in a cross-directional manner relative to thedirection of said sheet in said papermaking process, similar to the wayother sheet monitoring instruments such as brightness or basis weightprobes do.

In another embodiment, the fluorometer is configured so that on-linemeasurements can be taken.

A controller may be utilized to implement the above-referenced protocol.

One or more controllers are in communication with the fluorometer andare programmed with an algorithm to collect said fluorescencemeasurements, correlate the amount of fluorescence of the surfaceadditives when they are capable of fluorescing and/or inert fluorescenttracers on a sheet with the concentration of the surface additives in acoating on a sheet and/or thickness of a coating on a sheet; andoptionally adjust the amount of the surface additives added to thepapermaking process in response to the coating thickness on a sheetand/or concentration of the surface additives in a coating on a sheet inaccord with a predetermined protocol.

Adjusting the amount of the surface additives added to the papermakingprocess in response to the coating thickness on a sheet and/orconcentration of the surface additives in a coating on a sheet can bedone in various ways.

As stated above, a controller can implement this response or it can bedone manually through a papermaking process operator.

The adjustment can be done by various means.

In one embodiment, adjustment can be done through the use of a sprayboom in which the feed rate of the surface additives to the paper sheetcan be adjusted.

In another embodiment, one could adjust additive feed ratesindependently in a plurality of zones across the sheet based onfluorescence readings by scanning a fluorometer in a cross-directionalmanner relative to the direction of said sheet in said papermakingprocess.

In another embodiment, one could adjust papermaking process parameterssuch as sheet speed through the paper machine, and/or sheet moisture.

In another embodiment, the settings of a metering size press can beadjusted in response to the coating thickness on a sheet and/orconcentration of the surface additives in a coating on a sheet tomaintain a desired thickness or to maximize production tonnage rate orminimize over usage of additives or energy.

In another embodiment, the surface additives are added onto the sheet byone or more mechanisms: spray system, roller coater, blade coater, castcoater, rod coater, air knife coater, curtain coater, flexo coater,gravure coater, and screen coater.

In another embodiment, the apparatus may also include one or more partsof a paper machine in a papermaking process where the surface additivescome in contact with a sheet in the papermaking process.

In another embodiment, one can adjust the concentration of surfaceadditives in the apparatus in response to the fluorescence measurementsmade of one or more samples from the apparatus by a handheld, benchtop,in-line fluorometer, or a combination thereof.

With respect to measuring an apparatus that serves to hold or feed anaqueous composition into the papermaking process, the apparatuses may beof various varieties known to those of ordinary skill in the art. Inparticular, the apparatus may also include parts of the paper machinewhere the surface additives come in contact with the sheet.

In one embodiment, the apparatus is a chemical feeder or receptacle thatholds one or more chemicals.

In a further embodiment, the chemicals are surface additives. Withrespect to the types of chemicals being feed into the process, they canof various types including, but not limited to the ones discussed above.

The following example is not limiting.

EXAMPLES Protocol

Coat weight or coat thickness testing was performed following a standardtesting protocol. Several coating solutions containing various amountsof coating solids were applied to the surface of test sample sheets.Preferably, the solid content and inert fluorescent tracer ratio waskept constant for all solutions. The coat weight on each sample sheetcan be varied at the coating application time using various coatingtechniques. After drying, the dry coat weight, or pick-up, was measuredby weight difference. Every individual sample sheet was weighed beforeand after coating application and the dry coat weight calculated byweight difference. The fluorescence intensity of the dry starch film wasmeasured at several locations for a given sample sheet. The series offluorescence intensities were then averaged to yield a singlefluorescence intensity value for each sample sheet. Two differentfluorometers were used to measure the fluorescence intensity of eachsample sheet.

Example 1

A test was run following the above-described protocol with three starchsolutions containing increasing starch solids while maintaining thestarch and inert fluorescent tracer ratio constant. The substrate foreach test was an uncoated 21-point paperboard sheet. Each solution wasapplied on separate sample sheets at four different thicknesses via amanual application method. A fourth starch solution containing no inertfluorescent tracer was also applied to a series of sample sheets forcomparison with the traced solutions. The blank used in this trial wasan uncoated sample sheet.

FIG. 2 shows the starch dry coat weight (pick-up, in g/m²) plottedagainst the fluorescence intensity (in arbitrary units—relativefluorescence units (“RFU”)). Each point corresponds to an individualsample sheet. FIG. 2 shows that the measured fluorescence intensities ofthe entire series of sample sheets measured fall on a line along theplot area diagonal. The linear regression on all points shows veryclearly the direct and reliable correlation between the starch drypick-up and the amount of inert fluorescent tracer present in the layeras measured by fluorescence intensity. The trend line has a y-interceptvery close to zero and an R²-factor greater than 0.96. In a few cases,one point is significantly removed from the line. The same stray pointswere observed with two separate fluorometers, indicating that it is aproperty of the sample sheet, not an instrument related error. Suchpoints are likely due to defects in the starch layer on the paper web.This data demonstrates that coating defects can be detected with themethods of the claimed invention.

1. A method of monitoring and optionally controlling the addition of oneor more surface additives to a papermaking process comprising thefollowing steps: a. adding a known amount of a composition containingone or more surface additives to a papermaking process either alone orin known proportion with a known amount of one or more inert fluorescenttracers, wherein the composition containing the surface additives canonly be added alone when the surface additives are capable offluorescing; b. measuring the fluorescence of the surface additivesand/or one or more inert fluorescent tracers at a point prior to sheetformation; c. optionally measuring the fluorescence of the compositioncontaining the surface additives and/or one or more inert fluorescenttracers at a point subsequent to adding the surface additives and aftera sheet has been formed, wherein the surface additives can only bemeasured when they are capable of fluorescing and wherein fluorescenceis measured with a reflectance based fluorometer; d. correlating theamount of fluorescence of the surface additives when they are capable offluorescing and/or inert fluorescent tracers with the concentration ofthe surface additives, and if step c) occurs, then correlating theamount of fluorescence of the surface additives when they are capable offluorescing and/or inert fluorescent tracers on a sheet with theconcentration of the surface additives in a coating on a sheet and/orthickness of a coating on a sheet; and e. optionally controlling theaddition of the composition containing one or more surface additives toa papermaking process by adjusting the amount of the surface additivesadded to the papermaking process in response to the concentration of thesurface additives, and if step c) occurs, then optionally controllingthe addition of the composition containing one or more surface additivesto a papermaking process by adjusting the amount of the surfaceadditives added to the papermaking process in response to the coatingthickness on a sheet and/or concentration of the surface additives in acoating on a sheet.
 2. A method of monitoring and optionally controllingthe addition of one or more surface additives to a papermaking processcomprising the following steps: a. adding a known amount of acomposition containing one or more surface additives to a papermakingprocess either alone or in known proportion with a known amount of oneor more inert fluorescent tracers, wherein the composition containingthe surface additives can only be added alone when the surface additivesare capable of fluorescing; b. measuring the fluorescence of the surfaceadditives and/or one or more inert fluorescent tracers in an apparatusthat serves to hold or feed or apply an aqueous composition into saidpapermaking process; c. optionally measuring the fluorescence of thecomposition containing the surface additives and/or one or more inertfluorescent tracers at a point subsequent to adding the surfaceadditives and after a sheet has been formed, wherein the surfaceadditives can only be measured when they are capable of fluorescing andwherein fluorescence is measured with a reflectance based fluorometer;d. correlating the amount of fluorescence of the surface additives whenthey are capable of fluorescing and/or inert fluorescent tracers withthe concentration of the surface additives, and if step c) occurs, thencorrelating the amount of fluorescence of the surface additives whenthey are capable of fluorescing and/or inert fluorescent tracers on asheet with the concentration of the surface additives in a coating on asheet and/or thickness of a coating on a sheet; e. optionallycontrolling the addition of a composition containing one or more surfaceadditives to a papermaking process by adjusting the amount of thesurface additives added to the papermaking process in response to theconcentration of the surface additives; and if step c) occurs, thenoptionally controlling the addition of a composition containing one ormore surface additives to a papermaking process by adjusting theconcentration of the surface additives in the apparatus in response tocoating thickness on a sheet and/or concentration of the surfaceadditives in a coating on a sheet.
 3. The method of claim 2 wherein saidapparatus is a chemical feeder or receptacle that holds one or morechemicals.
 4. The method of claim 3 wherein said chemicals are surfaceadditives.
 5. The method of claim 1 wherein the fluorescence is measuredin a papermaking process after a paper is converted to a narrow web or asheet before end use.
 6. The method of claim 2 wherein the fluorescenceis measured in a papermaking process after a paper is converted to anarrow web or a sheet before end use.
 7. The method of claim 2 whereinthe surface additives are added onto the sheet by one or moremechanisms: spray system, roller coater, blade coater, cast coater, rodcoater, air knife coater, curtain coater, flexo coater, gravure coater,and screen coater.
 8. The method of claim 2 wherein the apparatus mayalso include one or more parts of a paper machine in a papermakingprocess where the surface additives come in contact with a sheet in thepapermaking process.
 9. The method of claim 2 further comprisingadjusting the concentration of the surface additives in the apparatus inresponse to the fluorescence measurements made of one or more samplesfrom the apparatus by a handheld fluorometer, benchtop fluorometer,in-line fluorometer, or a combination thereof.